As prior art technology, a waste heat utilization apparatus for an internal combustion engine is known as shown in Japanese Patent No. 2540738. In this apparatus, Rankine cycle is formed by using components of a refrigerating cycle, in which a compressor is also used as an expansion device for collecting waste heat from an internal combustion engine and supplying the collected power back to the internal combustion engine. In the above prior art apparatus, however, it is disadvantageous in that the collection of the waste heat from the engine is only possible when an operation of the refrigerating cycle is not necessary.
In the fluid machinery mentioned above, namely the fluid machinery (prior patent application No. 2003-19139) proposed by the same applicants, a compressor portion of the hybrid compressor is also used as an expansion device, wherein the compressor portion is operated as the compressor by an engine or a motor to compress refrigerant in a refrigerating cycle when the air-conditioning operation is necessary, while the compressor portion is operated as an expansion device to generate electric power at the motor when the air-conditioning operation is not necessary in such a way that the refrigerant of superheated steam is supplied to the compressor portion and the superheated steam is expanded in the compressor portion to generate rotational driving force. It should be noted here, however, the above mentioned fluid machinery is not a prior art to the present invention.